Bring the Ocean Home and Make Waves in a Bottle
What drives waves, and how do they move across oceans and seas?
Hosted by: 3M
Visit our Booth: Saturday, March 6, 2021, 12 p.m. - 4 p.m.
Recommended Grade: K, 1st, 2nd, 3rd, 4th, 5th
- An adult helper
- Two similar, clean, transparent bottles with caps (two-liter soda bottles work well)
- Vegetable oil, enough to fill one bottle two thirds full
- Food coloring (blue is a good choice)
- Pen and paper
- A workspace and covering material (such as an old towel) where spilled oil and water can easily be cleaned up
- Funnel for easier filling of the bottles (optional)
- Two small pieces of wax (Pieces cut off of a candle work well. Have an adult help you safely cut these.) (optional)
Have you ever noticed seagulls bobbing up and down on the ocean? You might have also seen surfers catch a wave that takes them to shore. Maybe you have floated on a lake, going up and down as a wave passed by. Or perhaps you have seen debris, such as driftwood, that has been washed up by waves. Water waves are fascinating—they come in all sizes, from a tiny ripple to monster waves that are 10 meters high. You have seen them, but do you know what drives them—and how they move across oceans and seas?
In this activity you will bring the ocean home and make waves in a bottle. You will also sharpen your observation skills and find out why some waves are slow, and others are fast.
Instructions and Procedures:
Visit https://www.3m.com/3M/en_US/gives-us/education/science-at-home/waves-in-slow-motion/ for the full instructions and explanations.
How does this activity connect to STEM and today's Girl Day theme of Moving Around: Land, Water, Air and Space?
This activity was all about moving water around and the science behind it.
Did you notice that water with oil on top produces surprisingly slow waves?
A wave moves because the extra weight of the liquid in the wave's peak pushes water from under the peak to places where the water is shallower. This happens in both bottles.
For the bottle with water and air, both the water and the air push on the deeper layers of water. Air is about one thousand times less dense than water, so when a wave passes by, deeper layers of water mainly get the weight of all the water piled up in the wave. The difference in weight between the crest and the trough (or lowest point) is the wave's driving force. In this scenario, the big difference in weight results in a fast-moving wave.
Similarly, for the bottle with water and oil, water and oil push on the deeper layers of water. Just like air, oil is less dense than water (about two-thirds as dense), so an amount of oil weighs less than the same amount of water. Thus, as water piles up in a wave, more water and less oil will weigh down on a spot underneath the wave peak. At the shallowest point of a wave, however, more oil and less water weighs down on the water below. As a result, the difference in weight of the liquids at a point under the crest and a point under the trough (or lowest point of the wave) is much smaller in this scenario, so the driving force of the wave is much smaller, although it still forces water to move from underneath the wave peak. In addition, the water and the heavier-than-air oil both have to be moved, so the liquids flow much more slowly than when the light air flows on top of water. What you observe is a wave on the water surface that travels much more slowly.
3M's Science at Home
Welcome to 3M's Science at Home video series: Fun and educational science experiments designed for students ages 6-12.
These simple, at-home experiments conducted by 3M scientists use common household items and are designed to reinforce core scientific principles. School systems, educators, parents, and caregivers are encouraged to use this educational content in virtual classrooms and at home.
Visit our website at 3M.com/scienceathome for more videos!